Fan base



FIG. 1 is a top perspective view of a fan base showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a side elevation view thereof, the opposite side being a mirror image of that shown; and,

FIG. 5 is a rear elevation view thereof.

The bottom view (not shown) forms no part of the claimed design. The subject matter shown in broken lines is for environmental purposes only and forms no part of the claimed design. 

The ornamental design for a fan base, as shown and described. 